E-SERIES
REFRIGERANT CHARGE LEVEL DETERMINATION PROCEDURE
For All Dual Evaporator Air Conditioning Systems with
Clutch Cycling Orifice Tube (CCOT) Systems Installed as the Front A/C Unit
Note: This test procedure cannot be used with Front TXV Evaporator Air Conditioning
Systems. Using this test procedure with Front TXV Evaporator Air Conditioning
Systems will
cause erroneous readings and will result in improper charge determination results.
Follow this test procedure as closely as possible to avoid an incorrect charge determination
test
and the wasting of time, resources, and money.
1. For the best possible results during this charge determination test, use .T.- Type
Thermocouples. Thermocouple readings are required on the EVAPORATOR INLET
TUBE, EVAPORATOR OUTLET TUBE, and RIGHT-CENTER DISCHARGE AIR
REGISTER.
Remove the evaporator, if possible, to make it easier to install the thermocouple, but note the
orientation of the core in the vehicle to insure that the thermocouples are placed in the proper
location or pre-mark the evaporator core prior to disassembly. Locate the evaporator
thermocouples on the refrigerant tubes as close to the evaporator core as possible. This is
especially important because the orifice tube is located in the evaporator inlet tube. Place the
thermocouples at either the 3 or 9 o.clock position on the evaporator tubes. Do not place the
thermocouples on the top or the bottom of the tubes, this will give erroneous readings and
will result in improper charge determination results. Use worm drive clamps to secure the
thermocouples to the tubes, keeping the worm drive on the opposite side of the
thermocouples. Insulate the worm drive clamps and thermocouples with cork tape or a
similar material. Place the register thermocouple in the right-center register about one inch
inside the duct. If the thermocouples touch the plastic register or ductwork, the temperature
readings will not be accurate.
NOTE: Refer to the sketch shown on Page 2.
2. Connect each thermocouple to a device that will display each temperature separately, or a
device that will record the temperatures.
3. Evaluate the A/C system under the following steady state conditions:
! The ambient temperature should be as close to 110° F as possible. The closer the
temperature is to 110° F, the better the test results.
! All windows must be fully open to provide a good thermal load on the A/C system.
! The A/C control must be set on the HIGH BLOWER speed, in the MAX A/C or
Recirculated Air position, and in the FULL COLD position.
! The vehicle must be driven at a steady speed of 40 MPH with the engine at normal
operating temperature. A straight flat road is the optimal condition for the charge
determination test and the cruise control will provide a constant speed without variation.
For the best results, the use of a climatic chamber or wind tunnel is recommended.
! There must be no restrictions in the refrigerant system to hamper refrigerant flow to all of
the evaporator cores.
! The Auxiliary A/C unit blower motors must be on the HIGHEST blower speed setting,
the Full Cold position, set the air flow to exit from the A/C outlets.
NOTE: There must be no restrictions of any kind during the refrigerant charge determination
test. If there are any shut-off devices installed in the system, they must be locked in the open
position as not to serve as a restriction.
4. When preparing the vehicle, evacuate the A/C system for at least one hour to remove any
unwanted trapped gasses. If any refrigerant oil is removed during this operation, replace it
before the test is started. Evaporators and accumulators can hold refrigerant for long periods
of time at room temperature and pressure. If necessary, operate the blower motor on the
HIGH BLOWER SPEED to heat the evaporator core and drive off the refrigerant that may
have settled in the core. Feel the bottom of the accumulator, if it is cold; place a heat gun or a
heat source by the accumulator in order to drive off any refrigerant that has accumulated.
When the accumulator is at least ambient temperature, continue with the vacuum decay test.
5. Perform a vacuum decay test on the system to determine if there are any small leaks in the
system. Evacuate the A/C system for at least one hour, turn the vacuum pump and the gauge
set off, and let the system set for at least 15 minutes. Note the reading on the gauge set. If
the vacuum holds for at least 15 minutes with no movement of the gage set needle, the
system is ready to charge. If the vacuum does not holds for at least 15 minutes, perform a
leak check test on the system and repeat this step until the vacuum holds for at least 15
minutes with no movement of the gage set needle.
6. Start with an initial refrigerant charge of 3.0 pounds (48 ounces). If the refrigerant charge is
less than 3.0 pounds (48 ounces), serious damage could occur to the compressor from high
discharge temperatures. Starting the test with more than 3.0 pounds (48 ounces), the system
could have already reached evaporator crossover and the system will have to be discharged,
evacuated, and the test re-started.
7. Run the vehicle until the EVAPORATOR INLET TUBE, EVAPORATOR OUTLET
TUBE, and RIGHT-CENTER DISCHARGE AIR REGISTER temperatures stabilize,
which is usually about 15 minutes. Record the temperatures every minute. If the
EVAPORATOR OUTLET temperature is higher than the EVAPORATOR INLET
temperature, the system is under-charged. Add two more ounces of refrigerant and restabilize the temperatures. Continue this procedure until the EVAPORATOR OUTLET
temperature is colder than the EVAPORATOR INLET temperature. When the
EVAPORATOR OUTLET temperature is colder than the EVAPORATOR INLET
temperature, the system has reached EVAPORATOR CORE CROSS-OVER. Add an
additional eight ounces of refrigerant for charge protection.
8. This is the refrigerant charge that the vehicle should contain for production.
NOTE: Refer to the data shown on Page 4.
The example data shown here serves only to illustrate that the discharge air temperatures
are approximately the average of the evaporator temperatures until crossover occurs. This
signals a fully charged system. The table shows the correct charge as 4.25 pounds.